CN117996218A - Multilayer all-solid-state battery and preparation method and application thereof - Google Patents

Abstract

The invention provides a multilayer all-solid-state battery, a preparation method and application thereof, wherein the multilayer all-solid-state battery comprises a positive electrode current collector, a first positive electrode layer, a second positive electrode layer, a first electrolyte layer, a second negative electrode layer, a first negative electrode layer and a negative electrode current collector which are sequentially stacked; the first positive electrode layer, the second positive electrode layer and the first electrolyte layer respectively independently comprise positive electrode side electrolyte materials, and the first negative electrode layer, the second negative electrode layer and the second electrolyte layer respectively independently comprise negative electrode side electrolyte materials; the first positive electrode layer and the second positive electrode layer have different compositions, and the first negative electrode layer and the second negative electrode layer have different compositions. The multilayer all-solid-state battery improves the compatibility inside the battery, improves the ion transmission between the electrode layer and the electrolyte layer and improves the performance of the all-solid-state battery by designing the multilayer structure differential electrode.

Description

A multi-layer all-solid-state battery and its preparation method and application

Technical Field

The present invention belongs to the technical field of batteries and relates to a multi-layer all-solid-state battery and a preparation method and application thereof.

Background technique

Lithium-ion batteries have become the first choice for consumer electronic batteries and new energy vehicle power batteries due to their advantages such as high energy density, long cycle life and no memory effect. However, lithium-ion batteries use flammable organic solvents as electrolytes, which poses a great safety risk. With the popularization of new energy vehicles, the number of spontaneous combustion incidents of new energy vehicles is also showing a rapid increase. Developing solid electrolytes to replace existing electrolytes and fundamentally avoiding the use of flammable organic solvents is an important way to improve the safety of lithium-ion batteries and achieve the intrinsic safety of lithium-ion batteries.

For example, CN 114744199A discloses an all-solid-state battery and a preparation method thereof, wherein the all-solid-state battery comprises a composite lithium negative electrode layer, an electrolyte layer, and a composite positive electrode layer in sequence. The surface of the lithium negative electrode is modified with Li ₃ N, which can not only improve the interface stability between the metal lithium negative electrode and the ceramic electrolyte, but also guide the uniform deposition and stripping of metal lithium during the charge and discharge process, and inhibit the formation of lithium dendrites.

However, problems such as the complex preparation process of existing all-solid-state batteries, poor compatibility between positive and negative electrodes of solid electrolytes, and poor electron and ion transport kinetics within electrodes are still bottlenecks restricting the development and application of all-solid-state batteries.

Based on the above research, there is a need to provide a multilayer all-solid-state battery, which has good compatibility between the positive and negative electrodes, improves the ion transmission between the electrode and the electrolyte layer, and enhances the rate performance of the all-solid-state battery.

Summary of the invention

The purpose of the present invention is to provide a multi-layer all-solid-state battery and its preparation method and application. The multi-layer all-solid-state battery improves the electrode kinetics and the compatibility of positive and negative electrode electrolytes by designing multi-layer structure differentiated electrodes, improves the ion transmission between the electrode and the electrolyte layer, and improves the rate performance of the all-solid-state battery.

In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a multilayer all-solid-state battery, the multilayer all-solid-state battery comprising a positive electrode current collector, a first positive electrode layer, a second positive electrode layer, a first electrolyte layer, a second electrolyte layer, a second negative electrode layer, a first negative electrode layer and a negative electrode current collector stacked in sequence;

The first positive electrode layer, the second positive electrode layer and the first electrolyte layer each independently include a positive electrode side electrolyte material, and the first negative electrode layer, the second negative electrode layer and the second electrolyte layer each independently include a negative electrode side electrolyte material;

The first positive electrode layer and the second positive electrode layer have different compositions, and the first negative electrode layer and the second negative electrode layer have different compositions.

The present invention designs a multi-layer structure differentiated electrode, adopts multi-layer positive electrode layers, negative electrode layers and electrolyte layers with different compositions, and adds solid electrolyte materials to both the positive electrode layer and the negative electrode layer. However, the solid electrolyte materials added to the positive electrode layer and the negative electrode layer are different. At the same time, in order to improve the internal compatibility of the battery, the electrolyte material added to the positive electrode layer is the same as the electrolyte material in the first electrolyte layer, and the electrolyte material added to the negative electrode layer is the same as the electrolyte material in the second electrolyte layer. This solves the compatibility problem of all-solid-state batteries, improves the ion transmission between the electrode and the electrolyte layer, and improves the rate performance of the all-solid-state battery.

Preferably, the thickness ratio of the first positive electrode layer to the second positive electrode layer, and the thickness ratio of the first negative electrode layer to the second negative electrode layer are independently (1-3):1, for example, can be 1:1, 2:1 or 3:1, but are not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Since the electrode layers of the present invention play different roles in order to improve the compaction density, capacity, dynamic performance, cycle performance and other performances of the battery, the thicknesses of different electrode layers preferably adopt the above ratio.

Preferably, the thickness ratio of the first electrolyte layer to the second electrolyte layer is (0.5-2):1, for example, it can be 0.5:1, 1:1, 1.5:1 or 2:1, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The first electrolyte layer and the second electrolyte layer of the present invention play a role in improving compatibility, and the thickness ratio of the first electrolyte layer and the second electrolyte layer is preferably within the above range.

Preferably, the thickness of the first electrolyte layer is 7-15 μm, for example, 7 μm, 9 μm, 12 μm or 15 μm, and the thickness of the second electrolyte layer is 7-15 μm, for example, 7 μm, 9 μm, 12 μm or 15 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the content of the positive electrode side electrolyte material in the second positive electrode layer is higher than the content of the positive electrode side electrolyte material in the first positive electrode layer.

In the second positive electrode layer of the present invention, which is close to the first electrolyte layer, the electrolyte material content is greater than that of the first positive electrode layer, which can improve the ion transmission capacity of the electrode and improve the electrode rate performance; the same is true for the negative electrode side.

Preferably, the positive electrode side electrolyte material content in the second positive electrode layer is 5-25wt%, for example, it can be 10wt%, 15wt%, 20wt% or 25wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the positive electrode side electrolyte material content in the first positive electrode layer is 1-12wt%, for example, it can be 3wt%, 5wt%, 7wt%, 9wt% or 11wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The electrolyte materials used in the present invention are all inorganic solid electrolyte materials.

Preferably, the cathode side electrolyte material includes a halide electrolyte and/or a sulfide electrolyte.

Preferably, the halide electrolyte used in the positive electrode side electrolyte material is preferably Li ₃ MB ₆ , M is any one of Y, Zr, In, Sc, Ta or La or a combination of at least two, B is selected from any one of Cl, Br or I or a combination of at least two, and the sulfide electrolyte used in the positive electrode side electrolyte material includes Li ₁₀ GeP ₂ S ₁₂ and element doping materials with the same structure.

Preferably, the content of the positive electrode active material in the second positive electrode layer is less than that in the first positive electrode layer.

The content of positive electrode active material in the second positive electrode layer of the present invention is less than that in the first positive electrode layer, so as to ensure the content of electrolyte material therein; the same is true for the negative electrode side.

Preferably, the positive electrode active material in the second positive electrode layer includes single crystal material or secondary granular material of nickel cobalt manganese oxide ternary positive electrode material and/or nickel cobalt manganese aluminum quaternary positive electrode material (single crystal material is selected for long cycle life battery cells, and secondary granular material is selected for high power battery cells).

Preferably, the positive electrode active material content in the second positive electrode layer is 70-90wt%, for example, 70wt%, 80wt% or 90wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the positive electrode active material in the first positive electrode layer includes any one of a cobalt manganese oxide ternary positive electrode material, a nickel cobalt manganese aluminum quaternary positive electrode material or a lithium-rich manganese-based positive electrode material, or a combination of at least two thereof, with a content of 85-95wt%, for example, 87wt%, 90wt%, 92wt% or 95wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the morphology of the positive electrode active material in the first positive electrode layer includes single crystal particles and secondary particles, which is a composite material of single crystal particles and secondary particles of any one or a combination of at least two of a lithium cobalt manganese oxide ternary positive electrode material, a nickel cobalt manganese aluminum quaternary positive electrode material or a lithium-rich manganese-based positive electrode material.

The first and second electrode layers of the present invention use different active materials and formulations. The first electrode layer close to the current collector side uses an electrode active material with low cost, high compaction density and high capacity, and the second electrode layer close to the electrolyte layer uses an electrode active material with good kinetics and long cycle life, so as to achieve a comprehensive improvement in the compatibility of battery cost, life and power performance.

Preferably, the binder content in the second positive electrode layer is less than the binder content in the first positive electrode layer.

Preferably, the binder content in the second positive electrode layer is 0.5-2wt%, for example, 0.5wt%, 1wt%, 1.5wt% or 2wt%, and the binder content in the first positive electrode layer is 1-3wt%, for example, 1.5wt%, 2wt%, 2.5wt% or 3wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the content of the conductive agent in the second positive electrode layer is less than that in the first positive electrode layer.

Preferably, the conductive agent content in the second positive electrode layer is 0-1wt%, for example, it can be 0wt%, 0.1wt%, 0.5wt% or 1wt%, and the conductive agent content in the first positive electrode layer is 0.5-3wt%, for example, it can be 1wt%, 2wt% or 3wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the content of the negative electrode side electrolyte material in the second negative electrode layer is higher than the content of the negative electrode side electrolyte material in the first negative electrode layer.

Preferably, the negative electrode side electrolyte material content in the second negative electrode layer is 2-30wt%, for example, it can be 5wt%, 10wt%, 20wt% or 30wt%, and the negative electrode side electrolyte material content in the first negative electrode layer is 0-25wt%, but does not include 0wt%, for example, it can be 5wt%, 10wt%, 20wt% or 25wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the negative electrode side electrolyte material includes a sulfide electrolyte.

The negative electrode electrolyte material of the present invention is selected from any one of Li _(6-x) PS _(5-x) X _(1+x) (X = Cl, Br, I, 0≤x≤0.6, for example, it can be 0, 0.4 or 0.6), xLi ₂ S·(1-x)P ₂ S ₅ (0.2≤x≤0.8, for example, it can be 0.2, 0.3 or 0.5) sulfide electrolyte or Li ₃ PS _4, which has stable reduction kinetics and does not contain metal elements other than Li, or a combination of at least two of them.

Preferably, the content of the negative electrode active material in the second negative electrode layer is less than the content of the negative electrode active material in the first negative electrode layer.

Preferably, the negative electrode active material in the second negative electrode layer includes any one of high-power artificial graphite, long cycle life artificial graphite, soft carbon or hard carbon, or a combination of at least two of them, with a content of 60-90wt%, for example, 70wt%, 80wt% or 90wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the negative electrode active material in the first negative electrode layer includes any one of artificial graphite, natural graphite, silicon-oxygen material or silicon-carbon material, or a combination of at least two of them, with a content of 70-95wt%, for example, 80wt%, 85wt%, 90wt% or 95wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the binder content in the second negative electrode layer is 0.5-2wt%, for example, 0.5wt%, 1wt%, 1.5wt% or 2wt%, the binder content in the first negative electrode layer is 1-3wt%, for example, 1.5wt%, 2wt%, 2.5wt% or 3wt%, and the binder content in the second negative electrode layer is less than the binder content in the first negative electrode layer.

Preferably, the conductive agent content in the second negative electrode layer is 0-1wt%, for example, 0wt%, 0.1wt%, 0.5wt% or 1wt%, the conductive agent content in the first negative electrode layer is 0.5-3wt%, for example, 1wt%, 2wt% or 3wt%, and the conductive agent content in the second negative electrode layer is less than that in the first negative electrode layer.

Preferably, the first electrolyte layer and the second electrolyte layer each independently further comprise a binder in an amount of 0.5-5wt%, for example, 1wt%, 3wt% or 5wt%, but not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the content of the electrolyte material on the positive electrode side in the first electrolyte layer and the content of the electrolyte material on the negative electrode side in the second electrolyte layer are independently 95-99.5wt%, for example, they can be 96wt%, 98wt%, 99wt% or 99.5wt%, but are not limited to the listed values, and other unlisted values within the numerical range are also applicable.

The binders used in the first positive electrode layer, the second positive electrode layer, the first electrolyte layer, the second electrolyte layer, the first negative electrode layer and the second negative electrode layer of the present invention independently include any one of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), styrene-butadiene rubber (SBR), nitrile rubber (NBR) or hydrogenated nitrile rubber (HNBR) or a combination of at least two thereof, and the conductive agents independently include any one of SP (conductive carbon black), CNT (carbon nanotube) or VGCF (vapor grown carbon fiber) or a combination of at least two thereof.

In a second aspect, the present invention provides a method for preparing a multilayer all-solid-state battery as described in the first aspect, the preparation method comprising the following steps:

(1) coating a first positive electrode layer mixed material, a second positive electrode layer mixed material and a first electrolyte layer mixed material on the surface of a positive electrode current collector to obtain a positive electrode;

(2) coating a first negative electrode layer mixed material, a second negative electrode layer mixed material, and a second electrolyte layer mixed material on the surface of the negative electrode current collector to obtain a negative electrode;

(3) assembling the positive electrode described in step (1) and the negative electrode stack described in step (2) to obtain the multilayer all-solid-state battery;

Step (1) and step (2) are performed in no particular order.

The present invention utilizes integrated three-layer coating technology to achieve integrated molding and manufacturing of the multi-layer structure of all-solid-state batteries, greatly simplifies the production process of all-solid-state batteries, and facilitates the mass production of all-solid-state batteries. It utilizes the mutual diffusion of the electrolyte layer and the electrode layer during the coating process to improve the ion transmission between the electrode and the electrolyte layer, thereby enhancing the rate performance of the all-solid-state battery.

The solvent used in the preparation method of the present invention when preparing the mixed material is selected from any one of NMP (N-methylpyrrolidone), toluene, xylene, trimethylbenzene, n-pentane, n-hexane, n-heptane or n-octane, or a combination of at least two thereof.

In a third aspect, the present invention provides an electronic device comprising the multi-layer all-solid-state battery as described in the first aspect.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention improves electrode kinetics by designing a differentiated electrode formula with a multi-layer structure, uses electrolyte materials matching the electrolyte layer in the electrode layer, the electrolyte material added to the positive electrode layer is the same as the electrolyte material in the first electrolyte layer, and the electrolyte material added to the negative electrode layer is the same as the electrolyte material in the second electrolyte layer, thereby achieving compatibility of the electrolyte materials; at the same time, the present invention utilizes an integrated three-layer coating technology, which, on the one hand, realizes the integrated molding and manufacturing of the multi-layer structure of the all-solid-state battery, greatly simplifies the production process of the all-solid-state battery, and facilitates the mass production of the all-solid-state battery; on the other hand, utilizes the mutual diffusion during the coating process of the electrolyte layer and the electrode layer to improve the ion transmission between the electrode and the electrolyte layer, thereby improving the rate performance of the all-solid-state battery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a multilayer all-solid-state battery according to Example 1 of the present invention;

1-positive electrode current collector, 2-first positive electrode layer, 3-second positive electrode layer, 4-first electrolyte layer, 5-second electrolyte layer, 6-second negative electrode layer, 7-first negative electrode layer, 8-negative electrode current collector.

Detailed ways

The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

Example 1

The present embodiment provides a multilayer all-solid-state battery as shown in FIG1 , wherein the multilayer all-solid-state battery comprises a positive electrode current collector 1, a first positive electrode layer 2, a second positive electrode layer 3, a first electrolyte layer 4, a second electrolyte layer 5, a second negative electrode layer 6, a first negative electrode layer 7 and a negative electrode current collector 8 stacked in sequence, wherein the first positive electrode layer 2, the second positive electrode layer 3 and the first electrolyte layer 4 comprise the same positive electrode side electrolyte material, and the first negative electrode layer 7, the second negative electrode layer 6 and the second electrolyte layer 5 comprise a negative electrode side electrolyte material;

The first positive electrode layer 2 includes 90wt% NCM811, 0.5wt% SP, 0.25wt% CNT, 7wt% Li ₃ YCl ₆ and 2.25wt% PVDF, and has a thickness of 70μm;

The second positive electrode layer 3 includes 86.5wt% NCM811, 0.2wt% SP, 0.1wt% CNT, 12wt% Li ₃ YCl ₆ and 1.2wt% PVDF, with a thickness of 30 μm, and a thickness ratio of the first positive electrode layer 2 to the second positive electrode layer 3 is 2.33:1;

The first electrolyte layer 4 includes 99 wt% Li ₃ YCl ₆ and 1 wt% PVDF, and has a thickness of 10 μm;

The first negative electrode layer 7 comprises 85 wt% of artificial graphite, 1 wt% of SP, 12 wt% of Li ₃ PS ₄ and 2 wt% of NBR, and has a thickness of 80 μm;

The second negative electrode layer 6 comprises 81.5 wt% of artificial graphite, 0.5 wt% of SP, 17 wt% of Li ₃ PS ₄ and 1 wt% of NBR, has a thickness of 35 μm, and a thickness ratio of the first negative electrode layer 7 to the second negative electrode layer 6 is 2.29:1;

The second electrolyte layer 5 includes 99 wt% of Li ₃ PS ₄ and 1 wt% of NBR, and has a thickness of 10 μm. The thickness of the first electrolyte layer 4 and the second electrolyte layer 5 is 1:1;

The method for preparing the multilayer all-solid-state battery comprises the following steps:

(1) adding the components of the first positive electrode layer 2, the second positive electrode layer 3 and the first electrolyte layer 4 into NMP according to the formula amount and dispersing them, coating them sequentially on the surface of the aluminum foil current collector on a coating machine using a three-layer coating die head and drying them to obtain a positive electrode;

(2) adding the components of the first negative electrode layer 7, the second negative electrode layer 6 and the second electrolyte layer 5 in order according to the formula amount to be uniformly dispersed in a p-xylene solvent, and then sequentially coating them on the surface of the copper foil current collector in a coating machine using a three-layer coating die head and drying them to obtain a negative electrode;

(3) The positive electrode described in step (1) and the negative electrode described in step (2) are die-cut to a set size, stacked in sequence, and then isostatically pressed to form a 1Ah soft-pack battery.

Example 2

The present embodiment provides a multi-layer all-solid-state battery, the multi-layer all-solid-state battery comprising a positive electrode current collector, a first positive electrode layer, a second positive electrode layer, a first electrolyte layer, a second electrolyte layer, a second negative electrode layer, a first negative electrode layer and a negative electrode current collector stacked in sequence, the first positive electrode layer, the second positive electrode layer and the first electrolyte layer comprising the same positive electrode side electrolyte material, the first negative electrode layer, the second negative electrode layer and the second electrolyte layer comprising a negative electrode side electrolyte material;

The first positive electrode layer includes 95wt% NCM811, 0.3wt% SP, 0.3wt% CNT, 1.4wt% Li ₃ YCl ₆ and 3wt% PVDF, and has a thickness of 30μm;

The second positive electrode layer includes 92wt% NCM811, 0.25wt% SP, 0.25wt% CNT, 5.5wt% Li ₃ YCl ₆ and 2wt% PVDF, has a thickness of 30 μm, and a thickness ratio of the first positive electrode layer to the second positive electrode layer is 1:1;

The first electrolyte layer includes 95wt% Li ₃ YCl ₆ and 5wt% PVDF, and has a thickness of 10 μm;

The first negative electrode layer comprises 95wt% artificial graphite, 0.5wt% SP, 1.5wt% Li ₃ PS ₄ and 3wt% NBR, and has a thickness of 35 μm;

The second negative electrode layer comprises 93wt% of artificial graphite, 0.25wt% of SP, 4.75wt% of Li ₃ PS ₄ and 2wt% of NBR, has a thickness of 35 μm, and a thickness ratio of the first negative electrode layer to the second negative electrode layer is 1:1;

The second electrolyte layer comprises 95 wt% of Li ₃ PS ₄ and 5 wt% of NBR, has a thickness of 20 μm, and the thickness of the first electrolyte layer and the second electrolyte layer is 0.5:1;

The method for preparing the multilayer all-solid-state battery comprises the following steps:

(1) adding the components of the first positive electrode layer, the second positive electrode layer and the first electrolyte layer into NMP according to the formula amount and dispersing them, coating them on the surface of the aluminum foil current collector in sequence on a coating machine using a three-layer coating die head and drying them to obtain a positive electrode;

(2) adding the components of the first negative electrode layer, the second negative electrode layer and the second electrolyte layer into a p-xylene solvent in order according to the formula amount and dispersing them evenly, and then coating them on the surface of the copper foil current collector in order in a coating machine using a three-layer coating die head and drying them to obtain a negative electrode;

(3) The positive electrode described in step (1) and the negative electrode described in step (2) are die-cut to a set size, stacked in sequence, and then isostatically pressed to form a 1Ah soft-pack battery.

Example 3

The present embodiment provides a multi-layer all-solid-state battery, the multi-layer all-solid-state battery comprising a positive electrode current collector, a first positive electrode layer, a second positive electrode layer, a first electrolyte layer, a second electrolyte layer, a second negative electrode layer, a first negative electrode layer and a negative electrode current collector stacked in sequence, the first positive electrode layer, the second positive electrode layer and the first electrolyte layer comprising the same positive electrode side electrolyte material, the first negative electrode layer, the second negative electrode layer and the second electrolyte layer comprising the negative electrode side electrolyte material;

The first positive electrode layer includes 85wt% NCM811, 1wt% SP, 1wt% CNT, 12wt% Li ₃ YCl ₆ and 1wt% PVDF, and has a thickness of 90 μm;

The second positive electrode layer includes 74wt% NCM811, 0.25wt% SP, 0.25wt% CNT, 25wt% Li ₃ YC _l6 and 0.5wt% PVDF, has a thickness of 30μm, and a thickness ratio of the first positive electrode layer to the second positive electrode layer is 3:1;

The first electrolyte layer includes 99 wt% Li ₃ YCl ₆ and 1 wt% PVDF, and has a thickness of 20 μm;

The first negative electrode layer includes 71wt% artificial graphite, 3wt% SP, 25wt% Li ₃ PS ₄ and 1wt% NBR, and has a thickness of 105 μm;

The second negative electrode layer comprises 68 wt% of artificial graphite, 1 wt% of SP, 30 wt% of Li ₃ PS ₄ and 1 wt% of NBR, has a thickness of 35 μm, and a thickness ratio of the first negative electrode layer to the second negative electrode layer is 3:1;

The second electrolyte layer comprises 99 wt% of Li ₃ PS ₄ and 1 wt% of NBR, has a thickness of 10 μm, and the thickness of the first electrolyte layer and the second electrolyte layer is 2:1;

The method for preparing the multilayer all-solid-state battery comprises the following steps:

(1) adding the components of the first positive electrode layer, the second positive electrode layer and the first electrolyte layer into NMP according to the formula amount and dispersing them, coating them on the surface of the aluminum foil current collector in sequence on a coating machine using a three-layer coating die head and drying them to obtain a positive electrode;

(2) adding the components of the first negative electrode layer, the second negative electrode layer and the second electrolyte layer into a p-xylene solvent in order according to the formula amount and dispersing them evenly, and then coating them on the surface of the copper foil current collector in order in a coating machine using a three-layer coating die head and drying them to obtain a negative electrode;

(3) The positive electrode described in step (1) and the negative electrode described in step (2) are die-cut to a set size, stacked in sequence, and then isostatically pressed to form a 1Ah soft-pack battery.

Example 4

The present embodiment provides a multi-layer all-solid-state battery, which is the same as that in Embodiment 1, except that the first positive electrode layer includes 86.5wt% of NCM811, 0.2wt% of SP, 0.1wt% of CNT, 12wt% of Li ₃ YCl ₆ and 1.2wt% of PVDF, and the second positive electrode layer includes 90wt% of NCM811, 0.5wt% of SP, 0.25wt% of CNT, 7wt% of Li ₃ YCl ₆ and 2.25wt% of PVDF.

Example 5

The present embodiment provides a multilayer all-solid-state battery, which is the same as that of Embodiment 1, except that the first negative electrode layer comprises 81.5wt% of artificial graphite, 0.5wt% of SP, 17wt% of Li ₃ PS ₄ and 1wt% of NBR, and the second negative electrode layer comprises 85wt% of artificial graphite, 1wt% of SP, 12wt% of Li ₃ PS ₄ and 2wt% of NBR.

Comparative Example 1

This comparative example provides a multi-layer all-solid-state battery, the multi-layer all-solid-state battery comprising a positive electrode current collector, a positive electrode layer, an electrolyte layer, a negative electrode layer and a negative electrode current collector stacked in sequence;

The positive electrode layer includes 90wt% NCM811, 0.5wt% SP, 0.25wt% CNT, 7wt% Li ₃ YCl ₆ and 2.25wt% NBR, and has a thickness of 95μm;

The negative electrode layer includes 85wt% artificial graphite, 1wt% SP, 12wt% Li ₃ PS ₄ and 2wt% NBR, and has a thickness of 105 μm;

The electrolyte layer includes 99 wt% Li ₃ PS ₄ and 1 wt% PTFE, and has a thickness of 20 μm;

The preparation method of the all-solid-state battery comprises the following steps:

According to the formula, the components of the positive electrode layer, the negative electrode layer and the electrolyte layer are uniformly dispersed in a toluene solution to form a uniform mixed material, which is then coated on the surface of the aluminum foil, the copper foil and the PET film in turn and dried to form the positive electrode, the negative electrode and the electrolyte membrane;

The above positive electrode, electrolyte membrane and negative electrode are cut into designed size, stacked and soft-packed, and then isostatically pressed to form a 1Ah soft-pack battery.

Comparative Example 2

This comparative example provides an all-solid-state battery, which is the same as Example 1 except that the first positive electrode layer of equal thickness is replaced by the second positive electrode layer, the first negative electrode layer of equal thickness is replaced by the second negative electrode layer, and the first electrolyte layer of equal thickness is replaced by the second electrolyte layer.

Comparative Example 3

This comparative example provides an all-solid-state battery, which is the same as Example 1 except that the mass of Li ₃ YCl ₆ in the first electrolyte layer is replaced by Li ₃ PS ₄ , and the mass of Li ₃ PS ₄ in the second electrolyte layer is replaced by Li ₃ YCl ₆ .

The all-solid-state batteries provided in the above embodiments and comparative examples were subjected to electrochemical performance tests, and the first efficiency of the test was: 0.2C discharge capacity divided by 0.05C first charge capacity;

1C capacity retention rate: 1C rate discharge capacity divided by 0.2C rate discharge capacity;

Room temperature cycle life: The number of cycles at 0.5C charge and discharge until the capacity retention rate reaches 80%.

The test results are shown in Table 1:

Table 1

From Table 1 we can see that:

It can be seen from Example 1 and Comparative Examples 1-2 that the present invention can improve battery performance through a multi-layer design. The positive electrode layer of Comparative Example 1 is only the first positive electrode layer, the negative electrode layer is only the first negative electrode layer, and the electrolyte layer is only the second electrolyte layer. The positive electrode layer of Comparative Example 2 is only the second positive electrode layer, the negative electrode layer is only the second negative electrode layer, and the electrolyte layer is only the first electrolyte layer. The performance of the obtained all-solid-state batteries is not as good as that of Example 1; It can be seen from Example 1 and Comparative Example 3 that the electrolyte materials in the first electrolyte layer and the second electrolyte layer of the present invention must be matched with the positive electrode side and the negative electrode side, otherwise the internal compatibility of the battery will be reduced, thereby reducing the performance of the all-solid-state battery; It can be seen from Example 1 and Examples 4-5 that different layers of the present invention are located in different positions and have different compositions. If the compositions of the first positive electrode layer and the second positive electrode layer are interchanged, or the compositions of the first negative electrode layer and the second negative electrode layer are interchanged, it will also affect the performance of the battery.

In summary, the present invention provides a multilayer all-solid-state battery and its preparation method and application. The multilayer all-solid-state battery improves the electrode kinetics and the compatibility of positive and negative electrode electrolytes by designing multilayer structure differentiated electrodes, improves the ion transmission between the electrode and the electrolyte layer, and improves the rate performance of the all-solid-state battery.

The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims (10)

1. A multi-layer all-solid-state battery, characterized in that the multi-layer all-solid-state battery comprises a positive electrode current collector, a first positive electrode layer, a second positive electrode layer, a first electrolyte layer, a second electrolyte layer, a second negative electrode layer, a first negative electrode layer and a negative electrode current collector stacked in sequence; The first positive electrode layer, the second positive electrode layer and the first electrolyte layer each independently include a positive electrode side electrolyte material, and the first negative electrode layer, the second negative electrode layer and the second electrolyte layer each independently include a negative electrode side electrolyte material; The first positive electrode layer and the second positive electrode layer have different compositions, and the first negative electrode layer and the second negative electrode layer have different compositions. 2. The multilayer all-solid-state battery according to claim 1, characterized in that the thickness ratio of the first positive electrode layer to the second positive electrode layer, and the thickness ratio of the first negative electrode layer to the second negative electrode layer are independently (1-3):1; And/or, the thickness ratio of the first electrolyte layer to the second electrolyte layer is (0.5-2):1; and/or, the positive electrode side electrolyte material content in the second positive electrode layer is higher than the positive electrode side electrolyte material content in the first positive electrode layer; And/or, the content of the positive electrode side electrolyte material in the second positive electrode layer is 5-25wt%; And/or, the positive electrode side electrolyte material content in the first positive electrode layer is 1-12wt%; And/or, the positive electrode side electrolyte material includes Li ₃ MB ₆ and/or Li ₁₀ GeP ₂ S ₁₂ , wherein M in Li ₃ MB ₆ is any one of Y, Zr, In, Sc, Ta or La or a combination of at least two thereof, and B in Li ₃ MB ₆ is any one of Cl, Br or I or a combination of at least two thereof. 3. The multilayer all-solid-state battery according to claim 1 or 2, characterized in that the content of the positive electrode active material in the second positive electrode layer is less than the content of the positive electrode active material in the first positive electrode layer; And/or, the positive electrode active material in the second positive electrode layer includes a nickel-cobalt-lithium manganese oxide ternary positive electrode material and/or a nickel-cobalt-manganese-aluminum quaternary positive electrode material, with a content of 70-90wt%; And/or, the positive electrode active material in the first positive electrode layer includes any one or a combination of at least two of a lithium cobalt manganese oxide ternary positive electrode material, a nickel cobalt manganese aluminum quaternary positive electrode material or a lithium-rich manganese-based positive electrode material, with a content of 85-95wt%. 4. The multilayer all-solid-state battery according to claim 1 or 2, characterized in that the binder content in the second positive electrode layer is less than the binder content in the first positive electrode layer; And/or, the binder content in the second positive electrode layer is 0.5-2wt%, and the binder content in the first positive electrode layer is 1-3wt%; and/or, the content of the conductive agent in the second positive electrode layer is less than the content of the conductive agent in the first positive electrode layer; And/or, the content of the conductive agent in the second positive electrode layer is 0-1 wt %, and the content of the conductive agent in the first positive electrode layer is 0.5-3 wt %. 5. The multilayer all-solid-state battery according to claim 1 or 2, characterized in that the negative electrode side electrolyte material content in the second negative electrode layer is higher than the negative electrode side electrolyte material content in the first negative electrode layer; and/or, the negative electrode side electrolyte material content in the second negative electrode layer is 2-30wt%, and the negative electrode side electrolyte material content in the first negative electrode layer is 0-25wt%, but excluding 0wt%; And/or, the negative electrode side electrolyte material includes any one of Li _(6-x) PS _(5-x) X _(1+x) , Li ₃ PS ₄ or xLi ₂ S·(1-x)P ₂ S ₅ , or a combination of at least two of them, wherein X in Li _(6-x) PS _(5-x) X _(1+x) is any one of Cl, Br or I, or a combination of at least two of them, and x in Li _(6-x) PS _(5-x) X _(1+x) satisfies 0≤x≤0.6, and x in xLi ₂ S·(1-x)P ₂ S ₅ satisfies 0.2≤x≤0.8. 6. The multilayer all-solid-state battery according to claim 1 or 2, characterized in that the content of the negative electrode active material in the second negative electrode layer is less than the content of the negative electrode active material in the first negative electrode layer; And/or, the negative electrode active material in the second negative electrode layer includes any one of artificial graphite, soft carbon or hard carbon or a combination of at least two thereof, with a content of 60-90wt%; And/or, the negative electrode active material in the first negative electrode layer includes any one of artificial graphite, natural graphite, silicon-oxygen material or silicon-carbon material or a combination of at least two thereof, with a content of 70-95 wt %. 7. The multilayer all-solid-state battery according to claim 1 or 2, characterized in that the binder content in the second negative electrode layer is 0.5-2wt%, the binder content in the first negative electrode layer is 1-3wt%, and the binder content in the second negative electrode layer is less than the binder content in the first negative electrode layer; And/or, the conductive agent content in the second negative electrode layer is 0-1wt%, the conductive agent content in the first negative electrode layer is 0.5-3wt%, and the conductive agent content in the second negative electrode layer is less than that in the first negative electrode layer. 8. The multilayer all-solid-state battery according to claim 1 or 2, characterized in that the first electrolyte layer and the second electrolyte layer further independently comprise a binder; And/or, the content of the electrolyte material on the positive electrode side in the first electrolyte layer and the content of the electrolyte material on the negative electrode side in the second electrolyte layer are independently 95-99.5 wt %. 9. A method for preparing a multilayer all-solid-state battery according to any one of claims 1 to 8, characterized in that the preparation method comprises the following steps: (1) coating a first positive electrode layer mixed material, a second positive electrode layer mixed material and a first electrolyte layer mixed material on the surface of a positive electrode current collector to obtain a positive electrode; (2) coating a first negative electrode layer mixed material, a second negative electrode layer mixed material, and a second electrolyte layer mixed material on the surface of the negative electrode current collector to obtain a negative electrode; (3) assembling the positive electrode described in step (1) and the negative electrode stack described in step (2) to obtain the multilayer all-solid-state battery; Step (1) and step (2) are performed in no particular order. 10. An electronic device, characterized in that the electronic device comprises a multi-layer all-solid-state battery according to any one of claims 1 to 8.